FIELD OF THE INVENTION
The invention generally relates to self-opening, collapsible, foldable and shortenable umbrellas.
The invention relates to a shortenable umbrella of a kind, comprising canopy rods which radiate from a stick and which are shortenable in at least a threefold manner. The stick being telescopic in at least two stages; a canopy cover supported by the canopy rods; a slider which is displaceable along the stick; struts pivotally connected at one end to the slider and at the other end at a first joint to a respective inner canopy rod part which, at its inner end, is pivotally connected to a ring fixed on the stick and, at its outer end is pivotally connected via a second joint to a respective control link. The control link having a lever arm extending inwardly of the second joint and connected at a third joint to an outer end of a respective control rod which is connected at its inner end at a fourth joint to a respective strut. Outer canopy rod parts each engaging an outer end of a respective control link at a fifth joint; and central canopy rod parts each consisting of inner and outer portions which are each pivotally connected at their adjacent ends to a respective slide element slidable along a respective one of the control links. The inner portion engaging the respective inner canopy rod part at a sixth joint inwardly of the second joint, and the outer portion engaging the inner end of a respective outer canopy rod part at a joint on a lever arm of the outer canopy rod part which extends inwardly of the fifth joint; whereby each control link and the respective central canopy rod part form the longer links. The part of the respective inner canopy rod part between the second and sixth joints and the lever arm of the respective outer canopy rod part form the shorter links, of a first parallelogram linkage which interacts with a second parallelogram linkage formed by that portion of the respective inner canopy rod part outwardly of the first joint and the respective control rod as longer links, and by a lever arm of the respective strut between the first and fourth joints and the lever arm of the respective control link as the shorter links.
An umbrella of this type is known, for example, from Federal Republic of Germany, Patent DE 3,809,873 A1. This construction has a relatively stable structure and a large protective canopy area with a small volume in the shortened, collapsed state. However, it is difficult to achieve a maximum stretching of the canopy rods with a corresponding maximum protective canopy parabola and unimpeded opening and closing operation. The canopy stretching is in practice therefore either not fully utilizable or it is achieved at the expense of user-friendly operation and careful maintenance of the umbrella.